My wife and kids were on CX845 last weekend... 2 in F and 1 in J (the flight was pretty full, although expertflyer never showed it go to F0 (was F1), CX never released another F award, so they were split between classes.
My wife and 9 year old were in row 1, the 12 year old was in row 11. All were fine with the arrangement, though the 12 year old found J seat "cramped" (was not the new CX J product). The 9 year old was on cloud 9 the whole trip. e-mailed me from 'The Cabin" in HKG about how wonderful it was. All the goodies she got made her backpack too heavy to carry! (PJ's, amenity kit, etc). They served her a real meal, turned her seat into a real bed, etc.
I'll be with them on the return flight in a couple of weeks... we have 2 F and 2 J, again rows 1 and 11. Wife and 9 year old will be in J and 12 year old and me in F (unless 12 year old agrees to swap with my wife). Return flight is currently showing as new J seats, but I kept them across aisles from each other rather then put them in center just in case CX swap equipment. I'm not even going to bother looking for 2 more F to open up. A curtain and one row of seats separating us is no big deal.
DAK